SAN JOSE, Calif.--I'm down at the Virtual Worlds conference here, and one of the most interesting things I've noticed is that everyone is trying to differentiate themselves from Second Life.

It actually makes sense. The attendees of this conference are largely people who are only recently coming to the concept of virtual worlds, and if there's one everyone's heard of, it's Second Life.

So, this differentiation is happening in two ways.

First, in panels, like the one I'm sitting in right now, titled "Blurring the lines between virtual and real worlds," audience members are asking the speakers, who are from a platform company called Icarus Studios, how their technology differs from that of Second Life.

Then, I turn to the conference program, and I see, on the inside back cover, an ad for There.com, a 3D social virtual world which, like Second Life, launched in 2003.

But There.com hasn't gotten one-hundredth the amount of media attention that SL has, and so the problem becomes: how do you position your virtual world when everyone knows about that other one?

In the case of the There.com ad, it's by pointing out, with big graphics, how it's different from SL.

For example, playing on the common fear of many companies interested in going into virtual worlds that Second Life is too beset by sexual content, the There.com ad has a big no-porn-allowed logo. It attempts to position itself as the safe virtual world by not so subtly talking up how it's very different from the Second Life model, in which anyone can create any kind of content, and many do, and which some fear is a moral free-for-all.

"There.com is a 'PG-13' environment, which means pornography, nudity and extreme language are strictly forbidden," the ad says. "Even though There.com is comprised of 98 percent user-generated content, each item actually goes through an internal approval process before it is released into the world."

The funny thing is that all this proactive differentiation is going on even as Linden Lab, the publisher of Second Life, is largely absent at this conference. In the past, the company has been the major sponsor at many conferences, and has, in some ways, overwhelmed people with its message.

Now, its message is definitely out there, even as all the far-lesser-known companies in the virtual-world space are desperate to try to make sure that, in the end, everyone knows how their product or service is different than Second Life.